Conventional methods for analyzing the deposition of agents, such as oral active agents used in dental care, involve incubating the agent with a substrate, washing the incubated substrate, and then subjecting it to solvent extraction. Subsequently, the extract is analyzed using high-performance liquid chromatography (HPLC) to provide an indirect quantification of the deposited agent. In a particular type of such an analysis, oral active agents such as Triclosan, either in neat solutions or in dentrifrice formulations, are incubated with saliva-coated hydroxyapatite disks used to model hard tissue substrates, prior to performing solvent extraction on the disk.
The solvent-extraction/HPLC method, however, has limitations. For example the method robes on the indirect analysis of an extract rather than the direct analysis of the surface onto which the agent is deposited. As a result of the extraction and subsequent HPLC steps, the analysis often takes considerable time. Moreover, the method relies on the use of an extracting agent which may not always be compatible with a given agent/substrate system (e.g., may decompose or adversely affect, for example by reaction with, the agent to be analyzed or otherwise influence the form of the agent).
Therefore, a need exists in the art for methods that can efficiently analyze or characterize the rate or amount of deposition of an agent onto a substrate. Ideally, such methods can be performed via direct analysis of the agent/substrate system and provide fast results.